Yu.B. Udalov

New continuous wave infrared Ar‐Xe laser at intermediate gas pressures pumped by a transverse radio frequency discharge

An atomic Xe laser with a transverse rf excitation has been operated in a cw mode in the intermediate pressure regime. The laser output spectrum consisted of 5 Xe lines with wavelengths of 2.03, 2.63, 2.65, 3.37, and 3.51 μm. The unoptimized total output power of 330 mW was obtained for a gas mixture Ar:He:Xe=59:40:1 at a pressure of 85 Torr and a rf input power of 150 W and excitation frequency of 121 MHz.

Generation of powerful electron beams in a dense gas with a dielectric-barrier-discharge-based cathode

An electron beam source based on a dielectric barrier discharge and a perforated anode working in a dense gas is described. Electron beams with current densities up to 60 A/cm2 and pulse durations of 150 ns were generated. Stable operation of the device at a repetition frequency of 200 Hz has been demonstrated.

Continuous wave near‐infrared atomic Xe laser excited by a radio frequency discharge in a slab geometry

Near‐infrared atomic Xe laser lines have been generated from an Ar:He:Xe laser gas mixture excited by a radio frequency (rf) discharge in a slab geometry. A maximum continuous wave (cw) output power of 1.5 W (270 W/l) was obtained at an rf frequency of 125 MHz from a gas mixture containing Ar:He:Xe (50:49:1) at a total gas pressure of 90 Torr.

RF discharge in CO2 laser mixtures at moderate pressures

The voltage-power characteristics and spatial structure of an RF discharge in the mixtures of CO2 and N2 molecular gases with He at total pressures of tens of torr are studied. One-dimensional numerical simulations of an RF discharge are carried out within two approaches: (i) the distribution function and the related kinetic coefficients are assumed to be functions of the local reduced field, and (ii) the kinetic coefficients are functions of the electron mean energy, which is calculated with allowance for both electron heat conduction and diffusion. The latter approach is shown to better describe the existing experimental dependence of the discharge voltage and the phase shift between the discharge current and voltage on the driving power.

Theoretical and experimental investigation of a waveguide CO2 laser with radio-frequency excitation

A comprehensive experimental and theoretical study of the optimization of a continuous-wave radiofrequency (rf) excited CO2 waveguide laser is presented. The numerical simulation includes the modelling of the gas-discharge plasma parameters like the plasma impedance and energy deposition, the laser kinetics and finally the influence of the resonator feedback on the lasing process. Along with this theoretical study, an extensive experimental research program enabled us to optimize the laser performance of the CO2 waveguide laser. As a result, a total output power of 42 W and a specific output power of 1.1 W/cm were obtained.

Enhanced gain and output power of a sealed‐off rf‐excited CO2 waveguide laser with gold‐plated electrodes

The small‐signal gain and the laser output power have been measured in a cw sealed‐off rf‐excited CO2waveguide laser for two different electrodematerials, gold‐plated copper and aluminum, at several excitation frequencies, gas pressures and mixture compositions. In the case of the gold‐plated electrodes an enhancement of the gain up to a factor of 2 and the output power up to a factor of 1.4 with time at a frequency of 190 MHz and 60 Torr of 1:1:5+5% (CO2:N2:He+Xe) mixture is observed. This is believed to be the result of the goldcatalytic activities which are favored by increased electrode temperatures and helium rich gas compositions.

Spectral investigation of cw rf-pumped atomic Xe laser with a slab geometry

A radiofrequency excited atomic Xe slab laser with an active volume of 2 × 10 × 300 mm3 using a quartz envelope containing the laser-gas mixture shows a stable cw performance with an output power of almost 1 W. The free-running system oscillates, depending on gas composition and density, on several lines between 1.73 and 3.51 μm. Line competition phenomena are observed. Single-line oscillation yields more than 500 mW.

Spatial gain profiles of a continuous wave radio-frequency pumped atomic xenon laser

Spatially dependent small signal gain measurements in a continuous wave rf excited Ar–He–Xe (59.5/40/0.5) gas discharge are presented. Maximum values for the small signal gain of the 2.03 and 2.65μm xenon transitions of about 22% and 37%/cm, respectively, were obtained at a total pressure of 120 mbar, an input power per unit electrode area of 20 W/cm 2 and at a rf driving frequency of 115 MHz. With a spatial resolution better than 0.5 mm, a strongly inhomogeneous gain distribution in the transverse direction was measured.

Influence of the electric field frequency on the performance of a RF excited CO2 waveguide laser

An analysis is presented of the effect of the RF frequency on the active media of CO2 waveguide lasers. It is found that the characteristics are improved with increasing RF frequency because the space charge sheath width decreases with increasing excitation frequency. We also found that the sheath width decreases with the discharge current; this fact was never discussed before. The higher the exciting frequency the higher is the maximum input power of the discharge in the stable low current mode. It is attractive to extend the input power while keeping the discharge in this mode. Finally, a stabilizing excitation technique is described for the inherent unstable region of the discharge.

Catalyst enhanced high power radio frequency excited CO2 slab laser

A substantial improvement in the specific laser output power (up to 30%) and efficiency (up to 50%) of a radio frequency (rf) excited slab CO2 laser with a distributed gold catalyst is observed when a large amount of CO (more than 60% of CO2 concentration) is added to the laser gas mixture. A maximum output power of 160 W with an efficiency of 17% was obtained from a laser with an active volume of 2×15×370 mm3. Gas mixtures with a high CO concentration combined with a distributed gold catalyst also accelerate the start-up time of rf pumped CO2 lasers considerably.